This invention relates to film for use in the signage industry to reduce power and improve luminance uniformity.
Lighted signs are everywhere in modern countries. The sign can educate, entertain, inform, or warn the viewer. The sign can be designed for close or distant viewing. Lighting is provided to assure the viewer can see the message, particularly during dimly lit days or nighttime.
Lights require energy to power them. Modern countries readily can provide the power, but those who pay for the energy are always seeking more efficient delivery of the power and more efficient usage of the power. The energy required to power a lighted sign should not be wasted for economic and environmental reasons.
Lighted signs can be xe2x80x9cfront litxe2x80x9d or xe2x80x9cback litxe2x80x9d. The former typically include such signs as billboards or other displays where the light is shone from the perimeter of the sign at an angle toward the sign. The latter typically have a translucent surface through which the light is seen and on which the message or image is placed. Uniformity of light emanating from the translucent surface is important. Often, the translucent surface includes some element that diffuses the light to reduce the identification by the viewer of the point or linear source of the light within the sign housing. Moreover, typical backlit signage today allows less than 20% of the light to escape from inside the sign for viewing. Clearly, a more efficient lighting system is needed.
The lighted sign can be in any configuration: Light sources can be neon, fluorescent, incandescent, halogen, high intensity discharge (HID), light emitting diodes (LED), or light fibers. The sign can be integral to a building, mounted as a fixture on a building, freestanding, or a part of other apparatus or equipment. The light can be powered continuously, periodically, episodically, or irregularly. Whenever the sign is lighted, the power used should not be wasted.
The lighted sign can be any geometric configuration.
Lighted signs that have a perimeter shape of a complex geometry to convey the intended message are entirely different types of signs from lighted signs that rely on a Euclidean geometry with the intended message within the perimeter. In the industry, an example of the former type of sign is called xe2x80x9cchannel lettersxe2x80x9d and can generically be called xe2x80x9ccomplex shape lighted signs.xe2x80x9d The latter are called xe2x80x9csign cabinetsxe2x80x9d because the perimeter of the sign is irrelevant to the message being conveyed.
Nonlimiting examples of sign cabinets include rectangular, oval, circular, elliptical, and other Euclidean geometrical shapes. Nonlimiting examples of complex shape lighted signs include letters, profiles, silhouettes, characters, or any other shape desired by a customer that helps to advertise, educate, warn or the like.
Lighting of Euclidean geometric sign cabinets is more predictable than complex shape lighted signs, because even distribution of the light is quite difficult to obtain unless the light source has the substantially the same shape as the viewing area of the sign.
What the art of lighted signage needs is a material that can improve the efficiency of lighted signs and reduce the power consumption required to display a message in a lighted sign as well as improve the luminance uniformity of the sign. Particularly, lighted signage where the sign cabinets are a complex shape lighted sign needs significant improvement to both luminance efficiency and luminance uniformity.
One aspect of the invention is a complex shape lighted sign housing, comprising an interior surface of the complex shape lighted sign housing; and a film applied to at least a portion of complex shape of the interior surface, wherein the film provides both an increase in luminance efficiency and an increase in luminance uniformity over a sign housing of the same complex shape that does not have such film applied therein.
Preferably, the film is selected from the group consisting of a diffuse reflective film, a semi-specular reflective film, and a specular reflective film having a diffuse reflective film laminated thereto or a diffused coating coated thereto.
xe2x80x9cFilmxe2x80x9d means a thin, flexible sheet in existence prior to contact with sign housing.
xe2x80x9cDiffuse reflective filmxe2x80x9d means a film that is reflective without being a mirrored surface. xe2x80x9cReflectivexe2x80x9d is an adjective of the noun xe2x80x9cReflectivityxe2x80x9d which is expressed in an industrial standard established by the American Society for the Testing of Materials (ASTM) in Standard ASTM E1164-94, the publication of which is incorporated herein by reference.
xe2x80x9cLuminance uniformityxe2x80x9d means the lumens of light emanating from a translucent surface are substantially uniform in a large number of locations on the surface, yielding a sign that does not significantly identify the location(s) of light source(s) within the sign housing.
A film of the present invention applied to at least a portion of an interior surface of a lighted sign housing captures the lumens of light from the light source or those lumens of light reflecting back from a diffusing panel or sides and backs of the light cabinet and re-directs such light toward the viewer and provides luminance uniformity on the translucent surface of the sign housing.
Another aspect of the present invention is a lighted sign housing, comprising an interior surface of the housing; and a film applied to at least a portion of the interior surface, wherein the film comprises a diffuse reflective film having a reflectivity of at least 80% as measured using ASTM E1164-94 and selected from the group consisting of polyolefin films filled with white particles, blends of incompatible polymers, polyolefin multilayer films; microvoided polyolefin and polyester films; fluorinated polyolefin films; vinyl chloride polymeric films filled with white particles; acrylic films filled with white particles; polyolefin films co-extruded with ethylene-vinyl acetate films; and combinations thereof.
Another aspect of the present invention is a method of using a film for signage, comprising the steps of selecting a film according to its reflectivity as measured by ASTM E1164-94 and according to its luminance uniformity; and applying the film to at least a portion of an interior surface of a lighted sign housing.
A feature of the invention is the reflectivity of the film can be controlled to provide desired power consumption reductions and improved luminance uniformity according to the needs of those skilled in the art of signage construction.
An advantage of the present invention is improvement of luminance uniformity while also providing significant power reduction for a sign, such that both utility and aesthetics of a sign are addressed by a single element within the sign housing.